How do you measure kiln shell temperature in shadow areas?

Shadow areas

Kilnscan infrared scanners are non-contact thermal monitoring systems, designed to provide a complete temperature map of the outer shell of a kiln, by collecting the infrared radiation over a wide field of view (FOV).

In the illustration below: the FOV is represented by a light blue triangle, with the Kilnscan scanner at the outside vertex. With its capability to scan over angles from 90° up to 140°, Kilnscan can measure the temperatures over the full length of the kiln shell.

Shadow areas on kiln shell thermal map

Some obstacles, such as buildings, posts and pillars may often mask parts of the shell. Besides, as shown in the zoom thumbnails in the above picture, tyres and drive wheel seen through at some angle from the scanner also create measurement blind zones in their immediate vicinity. Overall, these masked zones are the “shadow areas”.

If there are a few small-size obstructions

In order to monitor the temperature over the full length of the kiln shell, with no dead zone, several thermal spot sensors, called shadow pyrometers, are installed in front of the shadow areas, close to the shell. They are connected to the KILNSCAN receiver unit which operates as a data hub and merges temperature information from all sensors, to display the complete, seamless thermal map of the kiln shell.

Up to 8 shadow pyrometers can be connected to KILNSCAN receiver unit. Each pyrometer can be aligned in front of the kiln to monitor a spot equivalent to the size of a single refractory brick in shadowed or concealed areas.

Shadow pyrometers are particularly convenient in complex access areas, as illustrated in the picture below, where a cooling air tube is masking a wide part of the shell to the thermal scanner. Only the addition of a shadow pyrometer can enable to monitor hot spots behind the tube.

Cooling air tube in front of the kiln shell

The above picture was taken during the commissioning of Kilnscan scanners for Tasek in Malaysia. In this typical complex configuration, the line of sight of each scanner was obstructed by several posts and pillars. In comparable configurations, the best recommended thermal monitoring solution involves 2 or 3 scanner heads. At Tasek plant, 3 KILNSCAN scanners, each with a field of view of 140 °, were installed in order to display a thermal map with no dead zone. In such specific cases, wide-angle scanners are aligned with an overlap in their line of sights. The thermal image is then reconstructed by combining the data from these two or three scanners, eliminating shadows for a perfect full monitoring of the shell.

2 thermal scanners configuration, with FOV overlapping

About Electro Optical Industries

Electro Optical Industries, is a global provider of photonics equipment for wide area surveillance, industrial thermography, and visible/infrared test and measurement applications, with 3 product lines:

- the SPYNEL series, day&night 360-degree cameras, provide unprecedented situational awareness on land or at sea. Automatically detecting and tracking both conventional and asymmetrical threats, they secure wide perimeters in real-time,

- EOI's rotary kiln scanners and cameras for industrial thermography are used by maintenance teams worldwide at hundreds of cement plants for the thermal monitoring of kiln shells and burners,